Recent anatomical studies have identified a region of cortex in the rat, termed postrhinal cortex, that may be homologous to the parahippocampal cortex of primates. In both monkeys and rats, the primary cortical afferents of this region arise from visual association cortex and visuospatial regions such as posterior parietal cortex, suggesting that this region is involved in visuospatial function. Consistent with this concept are preliminary findings indicating that the postrhinal cortex plays a role in specific aspects of spatial memory as well as visuospatial attention. The goal of the proposed research is to further explore the function of this circuitry in spatial cognition. Neuroanatomical methods will be used to examine in detail the topographical and laminar pattern of visuospatial input to the postrhinal cortex (Specific Aim 1), as well as the intrinsic organization of the visual association, posterior parietal, and postrhinal cortices (Specific Aim 2). Neurophysiological methods will be used to examine the encoding of visuospatial information in postrhinal cortex while rats perform a spatial memory task and a visuospatial precueing task designed to measure attentional function (Specific Aim 3). The proposed experiments will be conducted with the purpose of furthering our understanding of the role of medial temporal lobe structures in cognitive function. Findings from these studies may have direct bearing on the neurobiological bases of cognition in both normal and brain-damage humans.